Tuesday, 18 June 2013

Taxon of the Day: Cephalanthera

Cephalanthera damasonium (left) and C.austinia (right)

This week a species of orchid, not previously recorded, was found on the University of Reading campus not far from where the Catalogue of Life is maintained. Cephalanthera damasonium or White Helleborine, was found growing under a Lime tree near the campus library. The genus Cephalanthera is found mostly in Europe and Asia (with one exception see below) and although the White Helleborine and its relative the Red Helleborine (Cephalanthera rubra) are two of the rarest orchids found in the UK, both are more common elsewhere in their range. It has been suggested that the etymology of Cephalanthera originated from the Greek cephalo- meaning head, and antheros meaning anthers so denoting a group with round anthers. However, Taxon of the Day hasn't yet checked the validity of this assertion.

One species of Cephalanthera that is found a long way from the UK is Cephalanthera austiniae or the Phantom Orchid. This is the only species in the genus found in North America, it too is rare and is native to British Columbia with a spread as far south as California. Unlike the White Helleborine the entire plant is white due to a lack of chlorophyll, and is instead dependent on symbiotic mycorrhizae for its nutrition. The common name of this plant comes from its distinctive ghostly appearance and its preference of lurking, in the understories of old-growth forests, thus making it extremely difficult to find. In British Columbia it is probably the showiest, rarest wildflower you will come across and the photograph above has been taken in one of only three known locations.

The Catalogue of Life through the World Checklist of Selected Plant Families lists 23 species of Cephalanthera in the family Orchidaceae.